Akira Tsuge

Determination of trace inpurities high-purity aluminum oxide by inductively-coupled plasma atomic emission-spectrometry

Abstract Trace impurities (Ca, Cu, Fe, Mg, Mn, Na and Si) in 99.99% aluminum oxide were determined by inductively-coupled plasma atomic emission spectrometry (i.c.p./a.e.s.). The sample was fused with lithium carbonate/boric acid to determine Ca, Cu, Mg, Mn, Na and Si or dissolved in phosphoric/sulphuric acids to determine iron. Matrix effects on the calibration graphs for each element were studied: for accurate determinations, calibration solutions must contain lithium and boric acid (or aluminium and phosphoric and sulphuric acids for iron).

Quantitative Analysis of Powdery Sample by Diffuse Reflectance Infrared Fourier Transform Spectrometry: Determination of the α-Component in Silicon Nitride

An application of diffuse reflectance infrared Fourier transform (DRIFT) spectrometry to determine powdery sample with an unknown particle size has been proposed. The usefulness of this technique has been demonstrated for the analysis of the α-component in Si3N4 powders. The particle size of the α-component in Si3N4 powder could be determined by measuring the peak intensity ratio between two peaks (500 and 690 cm−1) on the DRIFT spectrum, and the concentration could be determined by comparing the peak intensity to that of standard α-Si3N4 with same particle size. The particle sizes and concentrations obtained by the DRIFT method were in good agreement with those obtained by the light-scattering method and x-ray diffractometry, respectively.

Determination of Silicon Dioxide in Silicon Carbide by Diffuse Reflectance Infrared Fourier Transform Spectrometry

Diffuse reflectance infrared Fourier transform spectrometry was applied to the determination of SiO2 in SiC powders. The main peaks of SiO2 were observed in the 1000–1250 cm−1 region. The peak intensities were estimated from the peak height at 1150 cm−1. The intensities were little affected by the particle sizes of SiC powders in the 1–9–μm region. The linear relationship between peak intensity and concentration was obtained in the concentration range of 0–5 wt% SiO2. The analytical curve was successfully used for the determination of SiO2 in a few commercial SiC powders.

Synthesis of intermetallic NiAl and Ni 3 Al fine powders through organometallic precursors

Fine powders of intermetallic NiAl and Ni 3 Al were synthesized through organometallic precursors, which were coprecipitated from aqueous solutions of NiCl 2 and AlCl 3 by the addition of ammonium benzoate and hydradinium monochloride as precipitants. Ni 3 Al and NiAl were synthesized by a two-step heat treatment of the precurors. Single phase powders of NiAl and Ni 3 Al with the particle size less than 3 μm were obtained above 1300 and 1400 o C, respectively

Laser ablation in a liquid medium as a technique for solid sampling

A new technique for solid sampling, laser ablation in a liquid medium, has been developed and evaluated. A solid sample was held in a liquid medium contained in a flat-bottomed beaker. Laser pulses from a Q-switched Nd:YAG laser were introduced from the bottom of the beaker and were focused on the surface of the solid sample. Both the vapour and the particles produced by the laser ablation were trapped directly by the surrounding liquid, and a suspension was formed. The technique offers both time and spatial separation of the sampling and introduction and excitation processes in the laser ablation. The morphological observation of trapped particles, the evaluation of trapping efficiency and fractional ablation, and the direct introduction of the suspension into an inductively coupled argon plasma were carried out. Nearly 100% trapping efficiency and the absence of fractional ablation were obtained.

Determination of Silicon Dioxide in Silicon Carbide by Photoacoustic Infrared Fourier Transform Spectrometry

Advanced ceramics are being investigated quite actively. The characterization of the materials used to make the ceramics is important to final product performance. We have previously reported an application of diffuse reflectance infrared Fourier transform (DRIFT) spectrometry to the determination of silicon dioxide (SiO2) in silicon carbide (SiC). The DRIFT technique was found to have a simpler application than that of transmission techniques, for the analysis of powdered solids, because DRIFT does not require the sample preparation of KBr disks or mineral oil mulls. However, the scattering caused by the analyte powder surface requires dilution of the SiC powder with KBr fine powder, to avoid distortion of the diffuse refractance spectrum. For quantitative work, this dilution requires accurate weighing and perfect mixing.

Silica coating at the nanometer level on an α-alumina fine powder

Alumina fine powder which adsorbed a given amount of water was dispersed in a hydrophobic solution of n-hexane and ethyl silicate with a small amount of surfactant such as fatty acid, alkyl amine or sorbitan monostearate (Span 60). Ultra-fine particles and a thin film of silica were formed on the alumina particles after being coated in the solution with stearic acid and stearylamine, respectively. The addition of Span 60 reduced the catalytic activity of stearic acid and stearylamine for the hydrolysis. The silica content of the powder after coating treatment in the presence of stearylamine was nearly equal to that calculated from the amount of water adsorbed on the alumina powder. This silica content was controllable up to 15 wt.% by adjusting the amount of adsorbed water.

Determination of impurities in titanium carbide and titanium nitride by inductively coupled plasma atomic emission spectrometry

Inductively coupled plasma atomic emission spectrometry was applied to the determination of impurities (Al, Ca, Co, Cr, Fe, Mg, Mn, Mo, Na, Nb, Ni, Si, V, W and Zr) in titanium carbide (TiC) and titanium nitride (TiN). A 0.5-g amount of the powder sample was decomposed with 7.5 ml of nitric acid and 2.5 ml of hydrofluoric acid in a PTFE jar. The matrix effects on the background levels and the emission intensities of the elements were compensated for by using matrix-matched standard solutions for calibration. The results showed that the proposed method was useful for the analysis of TiC and TiN samples.

A method for evaluation of the component uniformity of a powder mixture by micro Fourier transform infrared spectrometry

Abstract A method for evaluating the uniformity of a small volume of components of four kinds of zirconia and silica powder mixture in the range of 10 −3 to 10 −5 mm 3 was investigated using micro-Fourier transform infrared (micro-FTIR) reflectance spectrometry. Reflectance spectra (spot size 250 × 250μm 2 ) were taken from 10 different locations within a sample and the relative standard deviation (RSD) of the peak height ratio (1100 cm −1 : assign to Si-O vibration/600 cm −1 : assign to Zr-O vibration) was calculated for each sample. If the RSD value was below the error that accompanied the measuring method (about 3%), the sample was regarded as uniform. The above operation was repeated with diminishing spot size (80 × 80 and 25 × 25 μm 2 ) for each sample, and the relationship between the RSD values and measuring volume, which was estimated from spot size, was obtained. The least volumes (regarded as uniform) were obtained for each sample.

Preparation of a microporous cell by dissolution of core particles within a core-shell-type composite powder-preparation of titania or silica microporous cells

Core-shell-type composite powders were prepared by hydrolysis of titanium tetraisopropoxide or tetraethyl orthosilicate in a dispersion of core particles adsorbed with water in hexane. Microporous cells could be made of the composite powder dissolved within the core particles in acetic acid solution. The content of titania in BaCO33-TiO2 composite powder was controlled by the amount of water adsorbed. The pore volume of the microporous cell changed with the content of titania. BaCO3-TiO2 composite powder was heated at 600°C for 10 h and barium ions in the core particles were diffused to titania. Thus, microporous cells composed of the BaTiO3 ultrafine particles were prepared.